Backlight unit and liquid crystal display device including the same

ABSTRACT

A light emitting diode assembly includes: a light emitting diode (LED) printed circuit board (PCB) having a base layer, an insulating layer on the base layer and a circuit pattern layer on the insulating layer, the LED PCB including a plurality of through holes spaced apart from each other; and a plurality of light emitting diodes (LEDs) inserted into the plurality of through holes, respectively, from a bottom surface of the LED PCB, each of the plurality of LEDs including a lead contacting the circuit pattern layer.

This application claims the benefit of Korean Patent Application No.10-2011-0034708, filed on Apr. 14, 2011, which is hereby incorporated byreference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display device, andmore particularly, to a liquid crystal display device having a narrowbezel region due to a light emitting diode (LED) backlight unit.

2. Discussion of the Related Art

A liquid crystal display (LCD) device that has been widely used for atelevision or a monitor because of its superiority in displaying amoving image and high contrast ratio produces images by using opticalanisotropy and polarization properties of liquid crystal molecules. TheLCD device includes a liquid crystal panel that is composed of facingtwo substrates and a liquid crystal layer between the two substrates. Analignment direction of liquid crystal molecules in the liquid crystalpanel is changed by an electric field so that the liquid crystal panelcan produce difference in transmittance.

Since the LCD device is a non-emissive type display device, anadditional light source is required. Accordingly, a backlight unitincluding a light source is disposed under the liquid crystal panel. Thebacklight unit may be classified into a direct type and an edge typeaccording to a position of the light source. In the direct typebacklight unit, the light source is disposed under the liquid crystalpanel and the light from the light source is directly supplied to theliquid crystal panel. In the edge type backlight unit, a light guideplate is disposed under the liquid crystal panel and the light source isdisposed at a side of the light guide plate so that the light from thelight source can be indirectly supplied to the liquid crystal panelusing refraction and reflection in the light guide plate.

Here, one of a cold cathode fluorescent lamp (CCFL), an externalelectrode fluorescent lamp (EEFL) and a light emitting diode (LED) maybe used as the light source. Specifically, the LED has been widely usedas a light source for a display device because of its advantages such assmall size, low power consumption and high reliability.

FIG. 1 is a perspective view showing a light emitting diode assembly ofa backlight unit according to the related art, and FIG. 2 is across-sectional view showing a liquid crystal display device including abacklight unit according to the related art. In FIG. 1, a light emittingdiode (LED) assembly 29 includes a plurality of LEDs 29 a and an LEDprinted circuit board (PCB) 29 b where the plurality of LEDs 29 a aremounted. The plurality of LEDs 29 a area spaced apart from each other.Leads 29 a-1 are formed at both sides of each of the plurality of LEDs29 a and a circuit pattern 29 b-1 is formed on the LED PCB 29 b. Theleads 29 a-1 are electrically connected to the circuit pattern 29 b-1 bysoldering. A backlight unit 20 (of FIG. 2) of a liquid crystal display(LCD) device 1 (of FIG. 2) may include the LED assembly 29 as a lightsource.

In FIG. 2, an LCD device 1 includes a liquid crystal panel 10, abacklight unit 20, a main frame 30, a top frame 40 and a bottom frame50. The liquid crystal panel 10 displaying an image includes first andsecond substrates 12 and 14 facing and spaced apart from each other anda liquid crystal layer (not shown) interposed therebetween. The liquidcrystal panel 10 further includes first and second polarizing plates 19a and 19 b on outer surfaces of the first and second substrates 12 and14, respectively.

The liquid crystal panel 10 and the backlight unit 20 are integrated bythe main frame 30, the top frame 40 and the bottom frame 50. The mainframe 30 having a rectangular ring shape surrounds an edge portion ofthe liquid crystal panel 10 and the backlight unit 20. In addition, thetop frame 40 covers a front edge portion of the liquid crystal panel 10and the bottom frame 50 covers a rear surface of the backlight unit 20.

The backlight unit 20 is disposed under the liquid crystal panel 10. Thebacklight unit 20 includes a light emitting diode (LED) assembly 29, areflecting plate 25, a light guide plate 23 and a plurality of opticalsheets 21. The LED assembly 29 is disposed under the main frame 30 andthe reflecting plate 25 having a white color or a silver color isdisposed over the bottom frame 50. In addition, the light guide plate 23is disposed over the reflecting plate 25 and the plurality of opticalsheets 21 are disposed over the light guide plate 23.

The LED assembly 29 of the backlight unit 20 includes a plurality ofLEDs 29 a emitting a white-colored light and an LED PCB 29 b where theplurality of LEDs 29 a are formed. A temperature of the plurality ofLEDs 29 a increases according to an operating time and a brightness ofthe plurality of LEDs 29 a is changed according to the temperature ofthe plurality of LEDs 29 a. Specifically, when a heat generated by theplurality of LEDs 29 a is not efficiently dissipated, a color of lightemitted from the plurality of LEDs 29 a may be changed. In addition,brightness of the light emitted from the plurality of LEDs 29 a maydecrease and lifetime of the LED assembly 29 may be reduced.

Accordingly, the LED PCB 29 b is fabricated so that the heat can bedissipated from the plurality of LEDs 29 a. Although the heat may bedirectly dissipated from the plurality of LEDs 29 a to the external air,the heat dissipation efficiency from the plurality of LEDs 29 a to theexternal air is smaller than the heat dissipation efficiency from theplurality of LEDs 29 a through the LED PCB 29 b. As a result, since mostheat of the plurality of LEDs 29 a on the LED PCB 29 b is dissipatedfrom the plurality of LEDs 29 a through the LED PCB 29 b, the heatdissipation of the LED assembly 29 has a limitation.

The plurality of LEDs 29 a of the LED assembly 29 face an incidentsurface of the light guide plate 23 such that a top surface of each ofthe plurality of LEDs 29 a is spaced apart from the incident surface bya first gap distance A1 and a top surface of the LED PCB 29 b is spacedapart from the incident surface by a second gap distance A2. The secondgap distance A2 corresponds to a sum of the first gap distance A1 and awidth of each of the plurality of LEDs 29 a. The separation between theLED assembly 29 and the light guide plate 23 by the first gap distanceA1 is required for protecting the plurality of LEDs 29 a by preventingcontact between the incident surface and the plurality of LEDs 29 a evenwhen the light guide plate 23 expands toward the LED assembly 29 by aheat.

However, since the LED assembly 29 is separated from the light guideplate 23 by the first gap distance A1, the whole light from theplurality of LEDs 29 a of the LED assembly 29 does not enter theincident surface of the light guide plate 23 such that a portion of thelight is lost.

Recently, the LCD device having a wide display area and a narrow bezelregion has been widely researched for a portable computer, a desktopcomputer and a wall-hanging television. However, since the LED assembly29 is separated from the light guide plate 23 by the first gap distanceA1, it is difficult to reduce a width W of the bezel regioncorresponding to a sum of the first gap distance A1, the thickness ofeach LED 29 a and the thickness of the LED PCB 29 b in the LCD device 1.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a backlight unit and aliquid crystal display device including the same that substantiallyobviate one or more of the problems due to limitations and disadvantagesof the related art.

An advantage of the present invention is to provide a backlight unitwhere a gap distance between a plurality of LEDs and a light guide plateis reduced by forming the plurality of LEDs inside an LED PCB and aliquid crystal display device including the backlight unit.

Another advantage of the present invention is to provide a backlightunit where an incident efficiency of light to the light guide plate isimproved and a width of a bezel region is reduced and a liquid crystaldisplay device including the backlight unit.

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. These andother advantages of the invention will be realized and attained by thestructure particularly pointed out in the written description and claimshereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described, a lightemitting diode assembly includes: an LED printed circuit board (PCB)comprising from the top down a base layer, an insulating layer, acircuit pattern layer and a protecting layer, wherein the LED PCBincludes along its longitude direction a plurality of through holesspaced from each other; a plurality of LEDs, inserted from the bottom ofthe LED PCB into the plurality of through holes, respectively, whereinthe plurality of LEDs comprise leads on both sides of the plurality ofLEDs, wherein the plurality of LEDs are electrically connected to theLED PCB through the leads.

In another aspect, a light emitting diode assembly includes: a lightemitting diode (LED) printed circuit board (PCB) having a base layer, aninsulating layer on the base layer and a circuit pattern layer on theinsulating layer, the LED PCB including a plurality of through holesspaced apart from each other; and a plurality of light emitting diodes(LEDs) inserted into the plurality of through holes, respectively, froma bottom surface of the LED PCB, each of the plurality of LEDs includinga lead contacting the circuit pattern layer.

In another aspect, a liquid crystal display device includes: a backlightunit having a reflecting plate, a light guide plate over the reflectingplate, a light emitting diode (LED) assembly along at least one side ofthe light guide plate and a plurality of optical sheets over the lightguide plate; a liquid crystal panel over the backlight unit anddisplaying an image; a main frame surrounding an edge portion of theliquid crystal panel and the backlight unit; a top frame covering afront edge portion of the liquid crystal panel; and a bottom framecovering a rear surface of the backlight unit, wherein the LED assemblyincludes: an LED printed circuit board (PCB) having a base layer, aninsulating layer on the base layer and a circuit pattern layer on theinsulating layer, the LED PCB including a plurality of through holesspaced apart from each other; and a plurality of light emitting diodes(LEDs) inserted into the plurality of through holes, respectively, froma bottom surface of the LED PCB, each of the plurality of LEDs includinga lead contacting the circuit pattern layer.

In another aspect, a liquid crystal display device includes: a backlightunit having a light emitting diode (LED) assembly, a light guide plateover the LED assembly and a plurality of optical sheets over the lightguide plate; a liquid crystal panel over the backlight unit anddisplaying an image; a main frame surrounding an edge portion of theliquid crystal panel and the backlight unit; a top frame covering afront edge portion of the liquid crystal panel; and a bottom framecovering a rear surface of the backlight unit, wherein the LED assemblyincludes: an LED printed circuit board (PCB) having a base layer, aninsulating layer on the base layer and a circuit pattern layer on theinsulating layer, the LED PCB including a plurality of through holesspaced apart from each other; and a plurality of light emitting diodes(LEDs) inserted into the plurality of through holes, respectively, froma bottom surface of the LED PCB, each of the plurality of LEDs includinga lead contacting the circuit pattern layer.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

In the drawings:

FIG. 1 is a perspective view showing a light emitting diode assembly ofa backlight unit according to the related art;

FIG. 2 is a cross-sectional view showing a liquid crystal display deviceincluding a backlight unit according to the related art;

FIG. 3 is a plan view showing a light emitting diode printed circuitboard for a light emitting diode assembly of a backlight unit accordingto a first embodiment of the present invention;

FIG. 4 is a plan view showing a light emitting diode assembly of abacklight unit according to a first embodiment of the present invention;

FIG. 5 is a cross-sectional view taken along a line V-V of FIG. 4;

FIG. 6 is a cross-sectional view showing a light emitting diode assemblyof a backlight unit according to a second embodiment of the presentinvention;

FIG. 7 is an exploded perspective view showing a liquid crystal displaydevice including a light emitting diode assembly according to a firstembodiment of the present invention;

FIG. 8 is a cross-sectional view, respectively, showing a liquid crystaldisplay device including a light emitting diode assembly according to afirst embodiment of the present invention;

FIG. 9 is a plan view showing a light emitting diode printed circuitboard for a light emitting diode assembly of a backlight unit accordingto a third embodiment of the present invention;

FIG. 10 is a plan view showing a light emitting diode assembly of abacklight unit according to a third embodiment of the present invention;and

FIG. 11 is a cross-sectional view showing a liquid crystal displaydevice including a light emitting diode assembly according to a thirdembodiment of the present invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Reference will now be made in detail to embodiments of the presentinvention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, similar reference numbers will be used torefer to the same or similar parts.

FIG. 3 is a plan view showing a light emitting diode printed circuitboard for a light emitting diode assembly of a backlight unit accordingto a first embodiment of the present invention, and FIG. 4 is a planview showing a light emitting diode assembly of a backlight unitaccording to a first embodiment of the present invention.

In FIGS. 3 and 4, a light emitting diode (LED) printed circuit board(PCB) 180 having a longer side and a shorter side includes a pluralityof through holes 188 for a plurality of LEDs 190. The plurality ofthrough holes 188 are disposed along the longer side of the LED PCB 180and spaced apart from each other. Each of the plurality of through holes188 has a rectangular shape corresponding to each of the plurality ofLEDs 190. In another embodiment, each of the plurality of through holes188 may have various shapes according to the shape of each of theplurality of LEDs 190.

In addition, each of the plurality of through holes 188 has an areacorresponding to each of the plurality of LEDs 190. For example, an areaof each of the plurality of through holes 188 may be slightly greaterthan an area of each of the plurality of LEDs 190 so that the pluralityof LEDs 190 can be easily inserted into or extracted from the pluralityof through holes 188. Accordingly, the LED assembly 100 is formed byinserting the plurality of LEDs 190 into the plurality of through holes188 of the LED PCB 180. Each of the plurality of LEDs 190 iselectrically connected to the LED PCB 180 through leads 198.

FIG. 5 is a cross-sectional view taken along a line V-V of FIG. 4 andFIG. 6 is a cross-sectional view showing a light emitting diode assemblyof a backlight unit according to a second embodiment of the presentinvention.

In FIG. 5, the LED PCB 180 includes a base layer 181, an insulatinglayer 182 on the base layer 181, a circuit pattern layer 183 on theinsulating layer 182 and a protecting layer 184 on the circuit patternlayer 183. In addition, the plurality of through holes 188 are formed inthe LED PCB 180 and are disposed along the longer side of the LED PCB180. The LED assembly 100 includes the LED PCB 180 and the plurality ofLEDs 190 inserted into the plurality of through holes 188 of the LED PCB180.

Each of the plurality of LEDs 190 may include a light emitting portion(not shown) having an LED chip substantially emitting light, a lens (notshown) that surrounds and protects the light emitting portion anddiffuses the light from the light emitting portion and leads 198 forelectrically connecting the light emitting portion and an external powersource. For example, each of the plurality of LEDs 190 may have a pairof cathode leads 198 a and a pair of anode leads 198 b at both sidesthereof, respectively. As a result, at least one anode lead 198 a isformed at one side of each of the plurality of LEDs 190 and at least onecathode lead 198 b is formed at the other side of each of the pluralityof LEDs 190. The positions of the at least one anode lead 198 a and theat least one cathode lead 198 b may be switched.

The base layer 181 may include a metallic material having a relativelyhigh heat conductivity such as silicon (Si), zinc (Zn) and aluminum (Al)so that the heat from the plurality of LEDs 190 can be effectivelydissipated. The LED PCB 180 including the base layer 181 of a metallicmaterial such as silicon (Si), zinc (Zn) and aluminum (Al) may bereferred to as a metal printed circuit board (MPCB) or a metal coreprinted circuit board (MCPCB). Alternatively, the LED PCB 180 may be oneof an FR-4 (flame retardant composition 4) PCB having a heat conductionmaterial, a ceramic printed circuit board and a flexible printed circuitboard (FPCB).

The insulating layer 182 electrically separates the base layer 181 andthe circuit pattern layer 183. The circuit pattern layer 183 may includea metallic material such as copper (Cu) and contact the leads 198 ofeach of the plurality of LEDs 190 to supply an electric power from theexternal power source. As a result, the circuit pattern layer 183 of theLED PCB 180 receives the operation current for emitting light from theexternal power source and supplies the operation current to theplurality of LEDs 190.

The protecting layer 184 protects the circuit pattern layer 183 andprevents discoloration of the circuit pattern layer 183. The protectinglayer 184 is formed except for an boundary portion of each of theplurality of through holes 188 such that a portion of the circuitpattern layer 183 is exposed through the protecting layer 184. Theexposed portion of the circuit pattern layer 183 through the protectinglayer 184 is used for connection with the leads 198 so that the leads198 of each of the plurality of LEDs 190 can contact the circuit patternlayer 183 of the LED PCB 180. The protecting layer 184 may include aphotosensitive epoxy or a photo solder resist (PSR).

The plurality of LEDs 190 are inserted into the plurality of throughholes 188, respectively, of the LED PCB 180 and the leads 198 of each ofthe plurality of LEDs 190 contact the circuit pattern layer 183 of theLED PCB 180. In addition, the leads 198 of each of the plurality of LEDs190 are electrically connected to the circuit pattern layer 183 of theLED PCB 180 through a solder. Here, since a first thickness L1 of theleads 198 of each of the plurality of LEDs 190 is greater than a secondthickness L2 of the protecting layer 184 of the LED PCB 180, a portionof the leads 198 corresponding to difference (L1−L2) between the firstand second thicknesses L1 and L2 protrudes outside a bottom surface ofthe LED PCB 180. Accordingly, each of the plurality of LEDs 190partially protrudes from the bottom surface of the LED PCB 180.

A third thickness L3 of each of the plurality of LEDs 190 is smallerthan a fourth thickness L4 of the LED PCB 180. For example, the thirdthickness L3 may be about 0.8 mm and the fourth thickness L4 may beabout 1 mm. Accordingly, when the plurality of LEDs 190 are insertedinto the plurality of through holes 188 upwardly from a bottom surfaceof the LED PCB 180, a top surface of each of the plurality of LEDs 190is located at a lower position than a top surface of the LED PCB 180.Specifically, since the portion of the leads 198 of the plurality ofLEDs 190 protrudes outside the bottom surface of the LED PCB 180, thetop surface of each of the plurality of LEDs 190 is disposed furtherlower than the top surface of the LED PCB 180.

In addition, since the plurality of LEDs 190 are inserted into theplurality of through holes 188, respectively, the plurality of LEDs 190are disposed closer to the base layer 181. Since the base layer 181includes a metallic material, the heat from the plurality of LEDs 190may be further efficiently dissipated through the base layer 181. Sincethe heat from the plurality of LEDs 190 inserted into the plurality ofthrough holes 188 is dissipated through top and side surfaces of theplurality of LEDs 190, the heat dissipation is improved as compared withthe related art LED assembly. As a result, discoloration and displayquality degradation are prevented and lifetime of the plurality of LEDs190 is improved.

In FIG. 6, leads 298 of a plurality of LEDs 290 do not protrude outsidea bottom surface of an LED PCB 280. The LED PCB 280 includes a baselayer 281, an insulating layer 282 on the base layer 281, a circuitpattern layer 283 on the insulating layer 282 and a protecting layer 284on the circuit pattern layer 283. In addition, a plurality of throughholes 288 are formed in the LED PCB 280 and are disposed along thelonger side of the LED PCB 280. A lead groove 286 surrounding each ofthe plurality of through holes 288 is formed such that each of baselayer 281, the insulating layer 282 and the circuit pattern layer 283has a step difference.

An LED assembly 200 includes the LED PCB 280 and the plurality of LEDs290 inserted into the plurality of through holes 288 of the LED PCB 280.The base layer 281 may include a metallic material having a relativelyhigh heat conductivity such as silicon (Si), zinc (Zn) and aluminum (Al)so that the heat from the plurality of LEDs 290 can be effectivelydissipated. The LED PCB 280 including the base layer 281 of a metallicmaterial such as silicon (Si), zinc (Zn) and aluminum (Al) may bereferred to as a metal printed circuit board (MPCB) or a metal coreprinted circuit board (MCPCB). Alternatively, the LED PCB 280 may be oneof an FR-4 (flame retardant composition 4) PCB having a heat conductionmaterial, a ceramic printed circuit board and a flexible printed circuitboard (FPCB).

The insulating layer 282 electrically separates the base layer 281 andthe circuit pattern layer 283. The circuit pattern layer 283 may includea metallic material such as copper (Cu) and contact the leads 298 ofeach of the plurality of LEDs 290 to supply an electric power from theexternal power source. As a result, the circuit pattern layer 283 of theLED PCB 280 receives the operation current for emitting light from theexternal power source and supplies the operation current to theplurality of LEDs 290.

The protecting layer 284 protects the circuit pattern layer 283 andprevents discoloration of the circuit pattern layer 283. The protectinglayer 284 is formed except for the lead groove 286 of each of theplurality of through holes 288 such that the leads of each of theplurality of LEDs 290 correspond to the lead groove 286. Accordingly,the leads of each of the plurality of LEDs 290 contact the circuitpattern layer 283 in the lead groove 286. The protecting layer 284 mayinclude a photosensitive epoxy or a photo solder resist (PSR).

The plurality of LEDs 290 are upwardly inserted into the plurality ofthrough holes 288, respectively, of the LED PCB 280 from a bottomsurface of the LED PCB 280 and the leads 298 of each of the plurality ofLEDs 290 are disposed in the lead groove 286 of each of the plurality ofthrough holes 288. Accordingly, the leads 298 of each of the pluralityof LEDs 290 contact and are electrically connected to the circuitpattern layer 283 of the LED PCB 280 through a solder.

Since the leads 298 of each of the plurality of LEDs 290 are disposed inthe lead groove 286 of each of the plurality of through holes 288, theleads 298 do not protrude outside the bottom surface of the LED PCB 280.For example, the leads 298 may be flush with the bottom surface of theLED PCB 280. In addition, a depth M of the lead groove 286 may be thesame as a first thickness L1 of the leads 298 of each of the pluralityof LEDs 290. Alternatively, the depth M of the lead groove 286 may bethe same as a sum of the first thickness L1 of the leads 298 and thesolder (not shown).

A third thickness L3 of each of the plurality of LEDs 290 is smallerthan a fourth thickness L4 of the LED PCB 280. For example, the thirdthickness L3 may be about 0.8 mm and the fourth thickness L4 may beabout 1 mm. Accordingly, when the plurality of LEDs 290 are insertedinto the plurality of through holes 288 upwardly from the bottom surfaceof the LED PCB 280, a top surface of each of the plurality of LEDs 290is located at a lower position than a top surface of the LED PCB 280.

In addition, since the plurality of LEDs 290 are inserted into theplurality of through holes 288, respectively, the plurality of LEDs 290are disposed closer to the base layer 281. Since the base layer 281includes a metallic material, the heat from the plurality of LEDs 290may be further efficiently dissipated through the base layer 281. Sincethe heat from the plurality of LEDs 290 inserted into the plurality ofthrough holes 288 is dissipated through top and side surfaces of theplurality of LEDs 290, the heat dissipation is improved as compared withthe related art LED assembly. As a result, discoloration and displayquality degradation are prevented and lifetime of the plurality of LEDs290 is improved.

FIGS. 7 and 8 are an exploded perspective view and a cross-sectionalview, respectively, showing a liquid crystal display device including alight emitting diode assembly according to a first embodiment of thepresent invention.

In FIGS. 7 and 8, a liquid crystal display (LCD) device 300 includes aliquid crystal panel 310, a backlight unit 320, a main frame 330, a topframe 340 and a bottom frame 350. The liquid crystal panel 310displaying an image includes first and second substrates 312 and 314facing and spaced apart from each other and a liquid crystal layer (notshown) interposed therebetween. Although not shown, when the liquidcrystal panel 310 has an active matrix type, a gate line, a data line, athin film transistor (TFT) and a pixel electrode may be formed on aninner surface of the first substrate 312 referred to as a lowersubstrate or an array substrate. In addition, a color filter layer, ablack matrix and a common electrode may be formed on an inner surface ofthe second substrate 314 referred to as an upper substrate or a colorfilter substrate. The gate line and the data line cross each other todefine a pixel region and the TFT is connected to the gate line and thedata line. Further, the pixel electrode is connected to the TFT. Thecolor filter layer includes red, green and blue color filters eachcorresponding to the pixel region and the black matrix covers the gateline, the data line and the TFT. Moreover, the common electrode isformed on the color filter layer and the black matrix. The liquidcrystal panel 310 further includes first and second polarizing plates319 a and 319 b where a predetermined polarized light selectively passeson outer surfaces of the first and second substrates 312 and 314,respectively.

A printed circuit board (PCB) 317 is connected to at least one side ofthe liquid crystal panel 310 through a connecting means 316 such as aflexible circuit board (FPC) or a tape carrier package (TCP). The PCB317 may be bent toward a side surface or a rear surface of the mainframe 230 during integration.

When the TFT connected to the gate line is turned on by a gate signal ofa gate driving circuit, a data signal of a data driving circuit isapplied to the pixel electrode through the data line and an alignmentdirection of liquid crystal molecules of the liquid crystal layer ischanged by an electric field generated between the pixel electrode andthe common electrode. As a result, the liquid crystal panel 110 producestransmittance difference and displays images.

The backlight unit 320 is disposed under the liquid crystal panel 310.The backlight unit 320 includes a light emitting diode (LED) assembly100, a reflecting plate 325, a light guide plate 323 and a plurality ofoptical sheets 321. The LED assembly 100 is disposed along at least oneside of the main frame 330 and the reflecting plate 325 having a whitecolor or a silver color is disposed over the bottom frame 350. Inaddition, the light guide plate 323 is disposed over the reflectingplate 325 and the plurality of optical sheets 321 are disposed over thelight guide plate 323.

The LED assembly 100 of the backlight unit 320 includes a plurality ofLEDs 190 emitting a white-colored light and an LED PCB 180 where theplurality of LEDs 190 are inserted into a plurality of through holes 188(of FIG. 5) of the LED PCB 180. The LED assembly 100 may be fixed by anadhesion and the LED PCB 180 may contact an incident surface of thelight guide plate 323 so that the whole light from the plurality of LEDs190 can enter the light guide plate 323 through the incident surface.Since the whole light from the plurality of LEDs 190 is supplied to theliquid crystal panel 310 by refraction and reflection in the light guideplate 323 without light leakage, brightness of the LCD device 300 isimproved.

In addition, since the top surface of the plurality of LEDs 190 isdisposed inside the top surface of the LED PCB 180, the plurality ofLEDs 190 do not contact the light guide plate 323 even when the lightguide plate 323 expands toward the LED assembly 100 by an ambient heat.As a result, the plurality of LEDs 190 and the light guide plate 323 areprotected from the thermal expansion of the light guide plate 323.

In the LCD device 300, since the plurality of LEDs 190 are formed in theLED PCB 180, the bezel region of the LCD device 300 has a width Wcorresponding to a sum of the fourth thickness L4 (of FIG. 5) of the LEDPCB 180 and the difference (L1−L2) between the first and secondthickness L1 and L2 (of FIG. 5). Accordingly, the width W of the bezelregion is reduced as compared with the related art LCD device.

Moreover, when the LED assembly according to the second embodiment ofFIG. 6 is adopted, the bezel region of the LCD device has a widthcorresponding to fourth thickness L4 (of FIG. 6). Accordingly, the widthof bezel region is further reduced.

Although not shown, the LED assembly 100 may further include an LEDdriving integrated circuit (IC) for driving the plurality of LEDs 190.The reflecting plate 325 is disposed under the light guide plate 323 andreflects the light passing through a bottom surface of the light guideplate 323 toward the liquid crystal panel 310 to improve brightness andefficiency of the light. The light emitted from the plurality of LEDs190 enters the light guide plate 323 and is uniformly diffused in thewhole light guide plate 323 by total reflection so that a planar lightcan be supplied to the liquid crystal panel 310. For the purpose ofsupplying a uniform planar light, the light guide plate 323 may includea uniformity pattern on the bottom surface thereof. For example, one ofan elliptical pattern, a polygonal pattern and a hologram pattern may beformed on the bottom surface of the light guide plate 323 as theuniformity pattern to guide the light entering the light guide plate 323and the uniformity pattern may be formed by a printing method or aninjecting method.

The plurality of optical sheets 321 over the light guide plate 323 mayinclude a diffusing sheet and at least one collimating sheet. Theplurality of optical sheets 321 may diffuse or collimate the lightpassing through the light guide plate 323 to improve uniformity of theplanar light. As a result, the light from the plurality of LEDs 190becomes the planar light through the light guide plate 323 and theplanar light enters the liquid crystal panel 310 through the pluralityof optical sheets 321. Further, the liquid crystal panel 310 displays animage of high brightness using the planar light.

The liquid crystal panel 310 and the backlight unit 320 are integratedby the main frame 330, the top frame 340 and the bottom frame 350. Themain frame 330 having a rectangular ring shape surrounds an edge portionof the liquid crystal panel 310 and the backlight unit 320. In addition,the top frame 340 covers a front edge portion of the liquid crystalpanel 310 and the bottom frame 350 covers a rear surface of thebacklight unit 320.

A pad 360 may be formed along at least one side between the main frame330 and the light guide plate 323 of the backlight unit 320 to preventmovement of the light guide plate 323. Specifically, when the lightguide plate 323 expands due to the heat, the pad 360 prevents an edgeportion of the light guide plate 323 from being bent toward the liquidcrystal panel 310. The main frame 330 may be referred to as a guidepanel, a main support or a mold frame and the top frame 340 may bereferred to as a top case or a case top. In addition, the bottom frame350 may be referred to as a bottom cover or a lower cover.

FIG. 9 is a plan view showing a light emitting diode printed circuitboard for a light emitting diode assembly of a backlight unit accordingto a third embodiment of the present invention, and FIG. 10 is a planview showing a light emitting diode assembly of a backlight unitaccording to a third embodiment of the present invention.

In FIGS. 9 and 10, a light emitting diode (LED) printed circuit board(PCB) 480 having a longer side and a shorter side includes a pluralityof through holes 488 for a plurality of LEDs 490. The plurality ofthrough holes 488 are disposed along the longer side of the LED PCB 480and spaced apart from each other. Each of the plurality of through holes488 has an open rectangular shape whose one side coincides with thelonger side of the LED PCB 480 and that corresponds to each of theplurality of LEDs 490. In another embodiment, each of the plurality ofthrough holes 488 may have various shapes according to the shape of eachof the plurality of LEDs 490.

In addition, each of the plurality of through holes 488 has an areacorresponding to each of the plurality of LEDs 490. For example, an areaof each of the plurality of through holes 488 may be slightly greaterthan an area of each of the plurality of LEDs 490 so that the pluralityof LEDs 490 can be easily inserted into or extracted from the pluralityof through holes 488. Accordingly, the LED assembly 400 is formed byinserting the plurality of LEDs 490 into the plurality of through holes488 of the LED PCB 480. Each of the plurality of LEDs 490 iselectrically connected to the LED PCB 480 through leads 498.

FIG. 11 is a cross-sectional view showing a liquid crystal displaydevice including a light emitting diode assembly according to a thirdembodiment of the present invention.

In FIG. 11, a liquid crystal display (LCD) device 500 includes a liquidcrystal panel 510, a backlight unit 520, a main frame 530, a top frame540 and a bottom frame 550. The liquid crystal panel 510 displaying animage includes first and second substrates 512 and 514 facing and spacedapart from each other and a liquid crystal layer (not shown) interposedtherebetween. The liquid crystal panel 510 further includes first andsecond polarizing plates 519 a and 519 b where a predetermined polarizedlight selectively passes on outer surfaces of the first and secondsubstrates 512 and 514, respectively.

The backlight unit 520 is disposed under the liquid crystal panel 510.The backlight unit 520 includes a light emitting diode (LED) assembly400, a reflecting plate 525, a light guide plate 523 and a plurality ofoptical sheets 521. The LED assembly 400 is disposed along at least oneside of the main frame 530 and the reflecting plate 525 having a whitecolor or a silver color is disposed over the bottom frame 550. Inaddition, the light guide plate 523 is disposed over the reflectingplate 525 and the plurality of optical sheets 521 are disposed over thelight guide plate 523.

The LED assembly 400 of the backlight unit 520 includes a plurality ofLEDs 490 emitting a white-colored light and an LED PCB 480 where theplurality of LEDs 490 are inserted into a plurality of through holes 488(of FIG. 10) of the LED PCB 480. The LED assembly 400 may be disposed toface at least one side (an incident surface) of the light guide plate523. Since one side of each of the plurality of through holes 488 isopen, one side of each of the plurality of LEDs 490 is exposed. Here,the exposed one side of each of the plurality of LEDs 490 is disposed toface the liquid crystal panel 510. As a result, an opaque pad 560 isformed between the main frame 530 and the light guide plate 523 of thebacklight unit 520 more easily as compared with the first and secondembodiments.

Further, since the pad 560 is disposed over the exposed one side of eachof the plurality of LEDs 490 of the LED assembly 400 and the light guideplate 523, the pad 560 may guide the whole light from the plurality ofLEDs 490 to the incident surface of the light guide plate 523.

In addition, the LED assembly 400 may be fixed by an adhesion and theLED PCB 480 may contact an incident surface of the light guide plate 523so that the whole light from the plurality of LEDs 490 can enter thelight guide plate 523 through the incident surface. Since the wholelight from the plurality of LEDs 490 is supplied to the liquid crystalpanel 510 by refraction and reflection in the light guide plate 523without light leakage, brightness of the LCD device 500 is improved.

Although the LED assembly according to the present invention is appliedto an edge type backlight unit in the first to third embodiments, theLED assembly according to the present invention may be applied to adirect type backlight unit. In the LCD device having a direct typebacklight unit, since the LED assembly is disposed directly under thelight guide plate and the LED PCB contacts the rear surface of the lightguide plate, the whole light from the plurality of LEDs enters the lightguide plate through the rear surface (incident surface) of the lightguide plate. Further, he LED assembly according to the present inventionmay be applied to an LCD device having a main frame whose one side isopen.

Consequently, in a liquid crystal display device according to thepresent invention, since the plurality of LEDs are formed in the LEDPCB, a gap between the LED assembly and the light guide plate isreduced. Accordingly, the light from the plurality of LEDs enters theincident surface of the light guide plate without loss and the incidentefficiency of light is improved. In addition, a width of a bezel regionis reduced. Further, since the plurality of LEDs do not contact thelight guide plate due to the LED PCB even when the light guide plateexpands by heat, the plurality of LEDs and the light guide plate areprotected.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1-15. (canceled)
 16. A light emitting diode (LED) backlight assemblycomprising: a light emitting diode (LED) printed circuit board (PCB)having a base layer, an insulating layer and a circuit pattern layer,directly contacted with each other and arranged sequentially, andincluding a plurality of through holes spaced apart from each other; anda plurality of light emitting diodes (LEDs) having electrode leadscontacted with the circuit pattern layer and disposed in the pluralityof through holes, respectively, wherein the plurality of light emittingdiodes (LEDs) protrude from a bottom surface of the light emitting diode(LED) printed circuit board (PCB), without extending out from a topsurface of the light emitting diode (LED) printed circuit board (PCB).17. The light emitting diode (LED) backlight assembly according to claim16, wherein shapes of the base layer, the insulating layer and thecircuit pattern layer are the same.
 18. An apparatus comprising: a lightemitting diode (LED) assembly configured as an edge mount backlight fora display, said LED assembly having recessed LED lamps with respectiveconductive leads, said recessed LED lamps and conductive leads notprotruding beyond a bottom planar surface of said LED assembly; and alight guide plate with a side edge that directly abuts with said bottomplanar surface of said LED assembly in order to guide light from saidrecessed LED lamps via said bottom planar surface to pass through a topplanar surface of said light guide plate and resulting in a bezel widththat is reduced compared to a conventional LED assembly with protrudingLED lamps attached to a conventional light guide (plate) that is spacedapart from said conventional LED assembly, said LED assembly including abase layer of metallic material that allows heat from said recessed LEDlamps to dissipate.
 19. The apparatus of claim 18, wherein said LEDassembly has a height defined by a distance between said bottom planarsurface and a top planar surface, whereby said height corresponds tosaid bezel width of said display.
 20. The apparatus of claim 19, whereinsaid base layer is configured in consideration of said side edge of saidlight guide plate being directly abutted with said bottom planar surfaceof said LED assembly and thus comprised of at least one among silicon,zinc and aluminum.